An inertial measurement unit (“IMU”) is an electronic device that measures and reports a velocity, orientation, and gravitational forces of a craft using a combination of accelerometers, gyroscopes, and magnetometers. One type of IMU includes a spherical gimbal system. The spherical gimbal system includes two or more gimbal shells of decreasing size placed within each other, and an instrument mount including electronics located in the center of the spherical gimbal system. In operation, the electronics of the instrument mount of the gimbal system produce heat that can alter the operation of the gimbal system. In particular, accelerometers and gyroscopes used in instrument mounts for IMUs are highly sensitive to changes in temperature and thermal gradients. Consistent airflow can help mitigates the primary cause of temperature fluctuations (and thus navigation errors) within these systems.
Existing convection cooled solutions have used fans and shrouds attached to the gimbals and instrument mount or high flow external fans in an attempt to provide consistent cooling. Fans (typically small and very high speed 15,000-20,000 RPM) attached to the instrument mount can be blocked or shadowed by the gimbal shells and other components depending on the orientation of the system, thereby reducing the effectiveness of the cooling. Further, such fans can induce vibrations to the sensitive inertial instruments and are a source of structure-borne noise that reduces the accuracy of the electronics in the instrument mount. Gas conduction cooled systems eliminate the instrument mount fan at the expense of high gimbal mass and inertia. While effective thermally when consistent rotation rates are employed, such gas conduction cooled systems require larger bearings to support the loads and very precise machining to keep the gimbal gap variation to a few thousandths of an inch, leading to an increase in cost to manufacture.
Accordingly, there is a need for a system that effectively cools an IMU without affecting the operation of the IMU.